Many industries are trying to become more environmentally friendly. As a result, many companies try to use more natural materials in their products. Others try to use recycled materials. One industry that has been very active in recycling has been the carpet industry. Many carpet companies use recycled PET (polyethylene terephthalate) from soda bottles to manufacture carpet fibers.
There is also a great deal of interest in recycling old carpet. At the present time, there is no uniform method of recycling carpet. Recycled carpet has a variety of uses including but not limited to composite lumber in the form of decking and sheets, tile backer board roofing shingles, railroad ties, automotive parts, carpet cushion, etc.
Carpet basically has two components, the face fiber and the backing structure to which the face fibers are secured. The face fiber is the part of the carpet on which the consumer walks. It is the top surface of the carpet. There are four common face fibers in use today. These are Nylon 6, Nylon 6.6, polypropylene (also called olefin) and polyester. Each of the face fibers has completely different properties (of the listed), which is why each of the types of face fibers must be separated from other different face fibers. The backing to where the face fibers are secured is usually a different material. Typical backing materials include polyvinyl chloride, latex and polypropylene.
At the present time, most recycling processes used for carpet try to recycle the face fibers. It is much more difficult to deal with the backing. The backing is usually composed of one or two polypropylene scrims and usually an adhesive present in addition to the backing material itself. Each of these materials are frequently made from different polymeric materials that are difficult to recycle together and need to be separated.
In some recycling processes, the carpet is initially tested to identify the types of fibers. Once the recycler knows with which kind of carpet they are dealing, the face fiber is separated from the backing and the glue is stripped off the back of the carpeting. In one process described in U.S. Pat. No. 5,898,063, nylon polymers or nylon fibers are dissolved in a solvent at, at least, the dissolution temperature of the nylon in the solvent. The solvent containing the dissolved nylon is then removed from the remainder of the solid residue. Last, the solvent nylon solution is cooled to precipitate and recover the nylon. There are other types of chemical carpet recycling processes, including those shown in U.S. Pat. No. 7,067,613 to Mauldin, U.S. Pat. No. 6,610,769 to Blanpain and U.S. Pat. No. 6,379,489 to Goulet. Besides chemical recycling processes, there are shredding methods where shredded carpet is melted to be reused in another application. These patents include U.S. Published Patent Applications 2004/0048035 to Bailey, 2003/0075824 to Moore and U.S. Pat. No. 5,684,052 to Krishnan. Some other processes grind the carpet into small granules and then use air to separate the individual components into their constituent parts. These patents include U.S. Pat. No. 5,497,949 to Sharer, U.S. Pat. No. 7,635,099 to Meredith and U.S. Pat. No. 5,535,945 to Sferrazza. In U.S. Pat. No. 6,051,300 portions of the carpet are selected for grinding. These selected separate portions are melted after grinding for reuse.
A screen is used to separate ground particles of carpet materials in U.S. Pat. No. 6,250,575 to White and U.S. Pat. No. 6,155,020 to Deem. Costello et al., U.S. Pat. No. 6,059,207 is directed towards a process for recycling carpet selvage waste that employs a device for shearing the face fiber of a carpet using multiple beveling heads. The device contains four beveling heads encased in separate boxes each which include a rotating cutting device, a stationary cutting device and a vacuum hose. The beveling heads are situated at equal intervals and are placed so that they are adjacent to a central rotating drum that carries selvage waste along its outer surface. The device functions by contacting the moving selvage waste with the beveling heads to yield removed face fiber and a sheared selvage waste composite. The face fiber is ultimately removed to a face fiber storage bin through the vacuum lines attached to the respective box. (See column 9, lines 40-67).
Hoover, U.S. Published Patent Application 2009/0082476 is for a process where face yarn is shaved and the face shaved yarn is reduced in size. Contaminants are removed by mechanical screeners. The shaved face yarn is then melt filtered and then fiber spun.